Preparation of lactone polyesters



L. s, end.

United 2,890,208 PREPARATION OF LAQTONE POLYESTERS 18' Claims; (Cl. 260-78.3)

This invention relates to an improved process for polymerizing lactones to form polyesters that are useful as plasticizers.

The facility with which the various lactones react and polymerize upon reaction with an organic compound having at least one hydroxyl or amino radical, such a compound being referred to herein as a monoor polyfunctional initiator, to form polyesters having terminal hydroxyl groups has been found to vary considerably. Thus, for example, dimethyl and epsilon-methyl substituted epsilon-caprolactones are difiicult to react and polymerize, even 'with the use of strongly basic ester exchange catalysts, without causing the product to be discolored.

We have made the surprising discovery that the poly merization of lactones generally can be accelerated very much more, without incurring discoloration of the resulting polyesters, than had hitherto been thought possible and that such improvement in the polymerization of lactones applies specifically also to such difiicul-tly polymerizable lactones as epsilon-methyl-caprolactone and the various dimethyl-epsilon-caprolactones. In accordance with the invention, this improvement in the polymerization of lactones is brought about by carrying out the reaction in the presence of a catalytic amount of an organic tin compound or an organic salt of lead or manganese.

The tin compounds that are particularly desirable as catalysts inthe method of the invention becauseot their ability to promote the formation of virtually colorlesspolyesters in a very short reaction time are those of the general formulae-z X and,

X I Sn in which the Xs stand for alkyl, aryl, arallcyl and aryloxy radicals, and the Xs stand for alkyl, aryl, aralkyl, acyloxy, halogen and hydroxy radicals. The tin compounds that deserve special mentionbecause of their efiiciency in accelerating the reaction and producing virtually colorless polyesters are tetraphenyltin, tetraoctyltin, diphenyltin dilaurate, tri-n-butyltin hydroxide, tri-n-butyltin acetate, dimethyltin oxide, dibutyltinoxide, dilauryltin oxide, di-n-butyltin dichloride, and dioctyltin dichloride.

The organic, salts of lead and manganese that have been foundespecially effective as catalysts include lead acetate, manganese acetate, lead Z-ethylhexoate, lead salicylate and lead benzoate.

While the method of the invention is particularly useful in the polymerization of lactones that are difiicult and perhaps even impossible topolymerize by other means, it is also of considerable advantage in the polymerization of other lactones that are not difiicult to poly- Fatented June 9, 1959 merize. The methodhas the-unique distinction of not only reducing reaction time very substantially, i.e., from a matter of days and even-weeks to a few hours and even less, but alsoof minimizing and inmost instances avoiding discoloration of'the endproduct.

The lactone used as a starting material may be any lactone, or combination of lactones, preferably having six or more carbon atoms in the ring. The lactones preferred as starting materials in the method of the invent1on are those having the general formula:

stituents other than hydrogenon the ring are considered.

unsuitable for the purposes of the invention because of the tendency that polymers thereof have to revert to the monomer, particularly at elevated temperature. Unsubstituted epsilon-caprolactone, in which n is four and all the Rs are hydrogen, is derived from o-hydroxyhexanoic acid. Substituted epsilon-caprolactones, and mixtures thereof, are available by reacting a corresponding substituted cyclohexanone with an oxidizing agent such as peracetic acid, as described in copending application Serial No. 548,754, filed November 23, 1955. The cyclohexanones may be obtained from substituted phenols or by other convenient synthetic routes.

Among the substituted epsilomcaprolactones considered most suitable as starting materials in the method of the invention are the various monoalkyl epsiloncaprolactones such as the monomethyl-, monoethyl-, monopropyl-, monoisopropyl-, etc. to monododecyl epsilon-caprolactones; dialkyl epsilon-caprolactones in which the two alkyl groups are substituted on the same or different carbon atoms, but. not both on the epsilon carbon atom; trialkyl epsilon-caprolactones in which two or three carbon atoms in the lactone ring are substituted, so long as the epsilon carbonatom is not disubstituted; alkoxy epsilon-caprolactones such as methoxy and ethoxy epsilon-caprolactones; and cycloalkyl, aryl, and aralkyl epsilon-caprolactones such as cyclohexyl, phenyl and benzyl epsilon-caprolactones. Mixtures of substituted lactones and mixtures of substituted lactones with unsubstituted lactoneshave been found to be particularly desirable.

Lactones having more than six carbon atoms in the ring, e.g., zeta-enantholactone and eta-caprylolactone, may also be polymerized in accordance with the method of this invention.

The initiators that are preferred in the method of the invention are represented by the general formula in which R is an organic radical selected from the group consisting of aliphatic, cycloaliphatic, aromatic and beterocyclic radicals, y is a number equal to the functionality of the initiator, and the Ys stand for --O-, -NH- and -NR, R being alkyl, aryl, aralkyl or cycloalkyl. These include'monofunctional initiators such as alcohols and amines that have a reactive site capable of opening the lactone ring and adding it onto the initiator as an open chainwithout forming water of condensation, and polyfunctional-initiators such as polyols, polyamines, amino alcohols, and vinyl polymers, as well as amides, sulfonamides, hydrazones, semicarbazones and oximes having two or more such reactive sites.

Alcohols that are useful as monofunctional initiators include primary, secondary, and tertiary aliphatic alcohols such as methanol, ethanol, propanol, isopropanol, l-butanol, Z-butanol, tert.butanol, l-pentanol, 3-pentanol, tert.-amyl alcohol, l-hexanol, 4-methyl-3-pentanol, 2- ethyl-l-butanol, l-heptanol, 3-heptanol, l-octanol, Z-ethyl-l-hexanol, l-nonanol, 2,6-dimethyl-4-heptanol, 2,6,8- trimethyl-4-nonanol, 5-ethyl-2-nonanol, 7-ethyl-2-methyl- 4-undecanol, 3,9-triethyl-6-decanol, and lauryl alcohol; aromatic alcohols such as benzyl alcohol and phenyl methy carbinol; and cycloaliphatic alcohols such as cyclohexanol and tn'methylcyclohexanol.

Amines that are useful as monofunctional initiators include primary and secondary aliphatic amines such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, isobutyl, tert.-butyl, n-amyl, n-hexyl and Z-ethylhexylamine, as well as the corresponding dialkyl amines; aromatic amines such as aniline, ortho-toluidine, meta-toluidine, para-toluidine, and diphenylamine; cycloaliphatic amines such as cyclohexyland dicyclohexylamine; and heterocyclic amines such as pyrrolidine, piperidine, and morpholine.

Diols that are suitable as bifunctional initiators include glycols of the formula HO(CH ),,OH in which n equals 2 to 10, glycols of the formulae HO(CH CH O),,H and HO(CHCH CH O),,H in which n equals 1 to 40, 2,2-dimethyl-l,3-propanediol, 2,2 diethyl-3-propanediol, 3-methyl-l,5-pentanediol, N-methyland N-ethyl diethanolamines, various cyclohexanediols,

OH 4,4'-methylenebiscyclohexanol,

4,4'-isopropylidenebiscyclohexanol,

various xylenediols,

O H: H1 0 H various hydroxymethyl-phenylpropanols,

o H, o H

omcmomon: various phenylenediethanols,

CHgGHQOH CH OH OH various phenylenedipropanols,

CH, omomoH omomomofl and various heterocyclic diols such as 1,4-piperazine diethanol,

CHgCH:

Nomomon CHOHI Other suitable diols include polyoxyalkylated derivatives of difunctional compounds having two reactive hydrogen atoms. These difunetional compounds may contain primary or secondary hydroxyls, phenolic hydroxyls, primary or secondary amino groups, amido, hydrazino, guanido, ureido, mercapto, sulfino, sulfonamido, or carboxyl groups. They are obtainable by reacting diols of the class HO(CH ),,OH, where n equals 2 to 10, propylene glycol, thiodiethanol, xylenediols, 4,4'-methylenediphenol, 4,4-isopropylidenediphenol, and resorcinol; mercapto alcohols, like mercaptoethanol; dibasic acids, such as maleic, snccinic, glutaric, adipic, pimelic, sebacic, phthalic, tetrahydrophthalic, and hexahydrophthalic; phosphorous acid; aliphatic, aromatic, and cycloaliphatic primary monoamines, like methylarnine, ethylamine, propylamine, butylarnine, aniline, cyclohexylamine; secondary diamines, like N,N-dimethylethylenediamine; and amino alcohols containing a secondary amino group, like N-methylethanolamine, with alkylene oxides such as ethylene oxide, propylene oxide, l-butylene oxide, Z-butylene oxide, isobutylene oxide, butadiene monoxide, styrene oxide, and also mixtures of these monoepoxides.

The preparation of the polyoxyalkylated derivatives is illustrated by the reaction of 1,4-butanediol with ethylene oxide:

Further useful bifunctional initiators are polymers of monoepoxides obtainable by polymerizing with such catalysts as oxonium salts of hydrogen halides; metal or non-metal halides whose etherates are oxonium complexes; electrophilic metal or non-metal halides in the presence of hydrogen halides, acyl halides, or anhydrides of inorganic and organic acids; and inorganic acids or anhydrides thereof whose anions show little tendency to polarize. Polymers containing hydroxyl end-groups may be obtained by treating these products with alkaline reagents upon completion of the polymerization reaction. Among suitable monoepoxides for preparing such polymers are tetrahydrofuran, trimethylene oxide, propylene oxide, ethylene oxide, or mixtures thereof.

Higher functional alcohols suitable for initiating the polymerization of lactones include tn'ols such as glycerol, trimethylolpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol, N-triethanolamine, and N-triisopropanolamine; various tetrols like erythritol, pentaerythritol, N,N,N,N'-tetrakis (Z-hydroxyethyl) ethylenediamine,

HOCILCH, oH,oH,0H

NCH OH N HOCILGH; CH,GH,0H

and N,N,N',N' tetrakis( 2 hydroxypropyl) ethylenediamine;

CH3 C I HO JHCH CH HOE NCHgCHgN HO CH0 1 OHIOHOH C HI; H;

assume pentols, hexols, like dipentaerythritol and sorbitol; alkyl glycosides; and carbohydrates such as glucose, sucrose, starch, and cellulose.

Also suitable as polyols are the polyoxyalkylated derivatives of polyfunctional compounds having three or more reactive hydrogen atoms as, for example, the reaction product of trimethylolpropane with ethylene oxide in accordance with the reaction:

mellitic acid,

ooon

nooo coon nooo ooon coon andpyromellitic acid,

coon

'ooon nooo coon

and polyfunctional inorganic acids like phosphoric acid.

Difunctional amino alcohols capable of initiating the polymerization of lactones include aliphatic amino al-' cohols of the general formula HO(CH ),,NH where n equals 2 to 10, N-methylethanolamine,

E H O C HaCHaNH isopropanolamine,

H HCHgN Hg N-methylisopropanolamine,

on, on, no ononzNn aromatic amino alcohols like para-amino-phenethyl alcohol,

onmn on and para-amino-alpha-methylbenzylalcohol,

cHoHcn,

NE and various cycloaliphatic amino alcohols like 4-arninocyclohexanol Higher functional amino alcohols having a total of at least three hydroxy and primary or secondary amino groups that are suitable include diethanolamine, diisopropanolamine, 2-(2-aminoethylamino)ethanol H NCH CH NHCH CH OH 2-arr iino-2(hydroxymethyl)-1,3-propanediol,

NH, HOCH21-OH1OH nlon and 2-amino-2-methyl-1,3-propanediol NH, noonr-o onnon Suitable diamines include aliphatic diamines of the general formula H N(CH ),,NH monos'econdary diamines of the general formula R"NH(CH ),,NH and disecondary diamines of the general formula where n equals 2 to 10 and where R" is alkyl, aryl, aralkyl or cycloalkyl; aromatic diamines, like meta-phenylenediamine, para-phenylenediamine, toluene-2,4-diamine, toluene-2,6-diamine, 1,5-naphthalenediamine, 1,8-naphthalenediamine, meta-xylylenediarnine, para-xylylenediamine, benzidine, 3,3'-dimethyl-4,4-biphenyldiamine, 3,3'-dimethoxy-4,4'-biphenyldiamine, 3,3'-dichloro-4,4- biphenyldiamine, 4,4'-methylenedianiline, 4,4'-ethylenedianiline, 2,3,5,6-tetramethyl-para-phenylenediamine, 2,5- fluorenediamine, and 2,7-fluorenediamine; and cycloaliphatic diamines like 1,4-cyclohexanediamine, 4,4-methylenebiscyclohexylamine, and 4,4-isopropylidenebiscyclohexylamine, and heterocyclicamines such as piperazine, 2,5-dimethylpiperazine, and 1,4 bis(3-amino propyl) piperazine omen,

CHQO 5 Higher functional polyamines typical of those suitable for use in the method are: diethylenetriamine, triethylenetetrarnine, tetra-ethylenepentamine, diisopropylenetriamine, triisopropylenetetramine, tetraisopropylenepentamine, 1,2,5 benzenetriamine, toluene 2,4,6 triamine, 4,4',4"-methylidynetrianiline,

HMO-6H 7 and polyamines obtained by interaction of aromatic monoamines with formaldehyde or other aldehydes, for example:

N H: NH;

and other reaction products of the above general type, where R is H or alkyl.

Lactones will also react with and polymerize on vinyl polymers containing reactive hydrogen atoms in side groups along the polymer molecule, particularly the reactive hydrogen atoms in hydroxyl and primary and secondary amino groups. Such vinyl polymers may, for example, be obtained by copolymerization of ethylene and vinyl acetate followed by subsequent saponification of the acetate groups to yield polymers represented by the following formula:

3-butene-1,2-diol CH,=CHCHOHCH,OH, allyl alcohol, methallyl alcohol, 3-phenyl-3-butene-l-ol,

and vinyl ethers like diethylene glycol monovinyl ether CH =CHOCH CH OCH CH OH.

A monofunctional initiator is believed to open the lactone ring to produce an ester having one terminal hydroxyl group that is capable of opening further lactone rings and thereby of adding more and more lactone to the molecule. Thus, for example, the polymerization of epsilon-caprolactone initiated with a monoamine is believed to proceed as follows:

A polyfunctional initiator is believed to open the lactone ring in a similar manner but to produce an ester having several terminal hydroxyl groups that are capable of opening further lactone rings and thereby of adding more and more lactone to the molecule. Thus, for example, the polymerization of epsilon-caprolactone initiated with a diol is believed to take place primarily as follows:

wherein a is the total number of mols of lactone reacted per mol of initiator and b+c=a.

It will be apparent from these equations that the number of lactone residues in the final polyester will depend in large part upon the molar ratio of lactone to initiator.

The polymerization is, in accordance with the invention, carried out by heating a lactone, or combination of lactones, with an initiator in the presence of the catalyst. Generally, the catalyst should be present in a catalytically significant amount, i.e., between about 0.001 and about 1% by weight, based on the amount of lactone in the reaction mixture. The preferred range of concentration for, the catalyst is between about 0.01 and about 0.2%, this more'limited range being preferred because of the uniformly excellent results that are obtained. Very small concentrations below the preferred minimum of 0.01% are, however, effective in providing fairly satisfactory polymerization rates. Amounts in excess of the maximum preferred amount of 0.2% shorten reaction time and are not harmful, although amounts in excess of about 1% should be avoided in order to avoid discoloration of the polyester.

The temperature to which the reactants are heated may vary from about 50 to about 300 C. Temperatures above this range are to be avoided because of the instability of the reactants and the products'at such higher temperatures, whereas reaction temperatures below about 50 C. will result in prolonged reaction time. Temperatures within the range of about 200 C. are preferred because discoloration of the products is thereby avoided while a desirably rapid rate of reaction is retained.

The time of heating depends upon the particular combination of lactone and initiator, as well as upon the particular catalyst employed and its concentration. It is readily ascertainable for any given starting materials, catalyst, catalyst concentration and temperature conditions by following the progress of the polymerization with refractive index measurements. The reaction may be regarded as complete as soon as the refractive index becomes constant. Generally, the reaction time will vary from a few minutes to not more than forty-eight hours and more usually between about one and twenty-four hours.

It is preferable, in order to obtain a product of light color, to conduct the reaction in the absence of oxygen. This may be accomplished, for example, by operating in a partial vacuum or in the presence of an inert gas such as nitrogen, which may be passed through the reaction mixture. After the polymerization is completed, any unreacted monomer may be removed by applying a vacuum thereto at elevated temperature, e.g., a vacuum of 1 to 5 mm. mercury at 120 to C.

The proportion of lactone to initiator may vary widely depending upon the particular properties desired in the polyester or the products to be made therefrom. Where the polyester is to have substantially the properties of i a product having a succession of lactone residues, the

assaaos proportion of initiator to lactone may be very small, inasmuch as theoretically one molecule of initiator is sufficient toinitiate the polymerization of an infinite number of lacetone molecules. On the other hand, where a poly-functional initiator is used and it is desired that the polyester product be of a conjugated structure in which the random distribution of lactone residues and polyfunctional compound residues is more or less alternating or where the polyfunctional initiator is a high molecular weight material such as a polyethylene glycol or vinyl polymer, the relative proportions may be approximately equal.

The polyester polymerization products obtained in accordance with the invention have molecular Weights generally within the range of about 500 to about 12,000, bydroxyl numbers between about 15 and about 350, carboxylx numbers up to about 7 and preferably below 5, and at least one active terminal group, usually hydroxyl, the number of active terminal groups depending upon the functionality of the initiator.

In addition, the polyesters of the invention are eminently suitable as plasticizers in various resins, e.g., vinyl chloride-vinyl acetate resins, particularly if they are acylated in known manner to insolubilize the terminal hydroxyl groups and thus improve their resistance to extraction by water from resins with which they are combined.

As plasticizers, the polylactones of the invention have the unique advantage, hitherto so elusive in the development of plasticizers, of combining excellent low temperature performance, i.e., imparting good flexibility to resins even at temperatures below zero, with low volatility and high resistance to water and oil extraction. They are available as easily-pourable liquids, and are therefore susceptible to facile handling and mixing as compared with the highly viscous, non-pourable plasticizers heretofore available. At the same time, the plasticizers of the invention are non-toxic and light-stable.

In the following detailed examples, which are included to illustrate the best modes now contemplated for carrying out the invention, initiators, lactones and catalysts, of varying amounts and identities, were mixed and heated to a controlled temperature of 170 C. while a slow stream of nitrogen was passed through the mixture to exclude air and moisture, thus preventing discoloration of the polyester from oxygen. The hydroxyl and carboxyl numbers of the resulting polyesters were determined by the method described in Ind. Eng. Chem, Anal. Ed., vol. 17, page 394 (1945). The polymerization was followed by refractive index measurements at 30 0., the reaction being regarded as complete as soon as the index became constant. Example 1 was included to compare the effectiveness of representative organic tin catalysts used in accordance. with the invention with the effectiveness of a typical strongly basic ester exchange catalyst. The particular catalysts, the amounts used, the polymerization tirneand the molecular weight and color of the polyester products are indicated.

Example 1 Laetone 150 g. dimethyl-epsilon-caprolactones (mixture syn- 10 Example 2 Lactone 169 g. dimethyl-epsilon-caprolactones (same mixture as in Example 1).

Initiator 4.80 g. ethylene glycol.- Catalyst 0.09 dibutyltiu oxide. Reaction time 4.5 hours.

Hydroxyl number 48.0.

Carboxyl number 2.1.

Molecular weight 2170.

Color Colorless.

Examples 1 and 2. show the remarkably superior efficacy, with regard to color of the polyester and the reaction time, of dibutyltin oxide as compared with that of calcium methoxide in polymerizing dimethyl lactone mixtures.

Example 3 Lactone g. beta-, gamma-, and

deltamethyl-epsilon-caprolactones.

initiator 3.50 g. propylene glycol.

Catalyst 0.10 g. dibutyltin oxide.

Reaction time 2.0 hours.

Hydroxyl number 46.6.

Carboxyl number 0.7.

Molecular weight 2340.

Color Colorless.

Example 4 Lactone 300 g. beta-, gamma-, and deltamethyl-epsilon-caprolactones.

Initiator 250 g. polyethylene glycol (average molecular weight: 1000).

Catalyst 0.30 g. dibutyltin oxide.

Reaction time 3.0 hours.

Hydroxyl number 47.7

Carboxyl number 1.0.

Color White wax.

Example 5 Lactone 25 g. alpha and epsilonmethyl epsilon caprolactones (obtained from o-cresol) and 75 g. beta,

Color Light brown.

Example 7 Lactone 50 g. epsilon caprolactone and 50 g. beta-, gamma-, and delta-methyl-epsiloncaprolactones. Initiator 5.6 g. quinitol. Catalyst 0.10 g. dibutyltin oxide. Reaction time 2.0 hours. Hydroxyl number 50.1 Carboxyl number 1.0. Color Light yellow.

Example 8 Lactone 100 g. beta-and deltamethyl epsilon caprolactones. Initiator 4.65 g. hexarnethylenediamine. Catalyst 0.05 g. dibutyltin oxide. Reaction time 18 hours. Hydroxyl number 39.9. Carboxyl number 1.0. Color Yellow.

Example 9 Lactone 100 g. alpha and epsilonmethyl epsilon caprolactones and 250 g. beta-. gamma-, and deltamethyl epsilon caprolactones. Initiator 12.2 g. toluene-2,4-diamine. Catalyst 0.08 g. dibutyltin oxide. Reaction time 16 hours. Hydroxyl number 28.71 Carboxyl number 1.3. Color Brown.

Example 10 Lactone 90 g. epsilon-caprolactone,

90 g. alpha and epsilonmethyl epsilon caprolactones and 170 g. beta-, gammaand delta-methylepsilon-caprolactones.

Initiator 5.95 g. pentaerythritol. Catalyst 0.175 g. dilauryltin oxide. Reaction time 20 hours. Hydroxyl number 26.4 Carboxyl number 0.9. Color Yellow.

Example 11 Lactone 100 g. betaand deltamethyl epsilon caprolactones. Initiator 4.25 g. triisopropanolamine. Catalyst 0.05 g. dilauryltin oxide. Reaction time 17 hours. Hydroxyl number 34.9. Carboxyl number 1.3. Color Yellow.

Example 12 Lactone 100 g. gamma-methyl-epsiloncaprolactone. Initiator 3.50 g. N-(aminoethyl) ethanolamine. Catalyst .5 0.02 g. dibutyltin oxide. Reaction time 16 hours. Hydroxyl number 46.4,. Carboxyl number 1.9. Color Light brown.

12 Example 13 Lactone 50 g. octyl-epsilon-caprolactones (synthesized from a mixture of octylphenols obtained by alkylation of phenol with 2-ethylhexanol).

Initiator 1.45 g. ethylene glycol.

Catalyst 0.025 g. dibutyltin oxide.

Reaction time 45 hours.

Hydroxyl number 40.5.

Carboxyl number 0.9.

Color Brown.

Example 14 Lactone 29.6 g. octyl-epsilon-caprolac-' tones (same as in Example 13) and 35 g. epsilon-caprolactone.

and propyl-caprolactones (prepared from a xylenol fraction boiling at 224229 C.).

Initiator 9.13 g. trimethylol propane. Catalyst 0.2 g. dibutyltin oxide. Reaction time 21 hours. Hydroxyl number 28. Carboxyl number 0.9. Color Yellow.

Example 16 Lactone 139 g. mixture of substituted-epsilon-caprolactones (same as in Example 15) and 261 g. epsilon-caprolactone.

Initiator 11.6 g. ethylene glycol. Catalyst 0.2 g. dibutyltin oxide. Reaction time 5.5 hours. Hydroxyl number 48.3. Carboxyl number 1.9. Color Light yellow.

Example 17 Lactone 400 g. mixture of substituted-epsilon-caprolactones (prepared from commercial cresylic acid consisting of a mixture of cresols, xyenols and higher phenols and therefore having one-, two-, and three-carbon side chains at various positions on the ring).

Initiator 1,2,4-butanetriol. Catalyst 0.2 g. dibutyltin oxide. Reaction time 5.5 hours.

Hydroxyl number 41.4. Carboxyl number 0.9.

Color Light yellow.

Example 18 Lactone 139 g. mixture of substituted-epsilon caprolactones (same as in Example 17) and 261 g. epsilon-caprolactone.

Initiator 11.6 g. ethylene glycol. Catalyst 0.2 g. dibutyltin oxide. Reaction time 3 hours.

Hydroxyl number 49.2.

Carboxyl number 1.3.

Color Colorless.

asses-es Example 19 Lactone 130 g. mixture of alpha-, beta-,

gamma-, delta-, and epsilonepsilon methyl caprolactones (prepared from mixed mand p-cresols) and 270 g. epsilon-caprolactone.

Initiator 11.6 g. ethylene glycol.

Catalyst 0.2 g. dibutyltin oxide.

Reaction time 4.5 hours.

Hydroxyl number 49-.4. Carboxyl number.... 0.8.

Color Yellow.

Example 20 Lactone 300 g. mixture of methyl-epsiloncaprolactones (same as in Example 19). Initiator 28.1 g. triethanolamine and ethylene oxide adduct prepared by slowly adding 262' g. ethylene oxide. to 298. g. triethanolamine at. 120130 C. over a period of seven hours, followed by removal of a small amount of unreacted ethylene oxide under reduced pressure. The adduct had a hydroxyl number of 580.

Catalyst 0.15 g. dibutyltin oxide.

Reaction time 6 hours.

Hydroxyl number 48.9.

Carboxyl number..- 1.3.

Color Yellow.

Example 21 Lactone 600 g. mixture of methyl-epsiloncaprolactones (same as in Example l9). Initiator 36 g. 2-ethyl-1-hexanol. Catalyst 0.3 g. dibutyltin oxide. Reaction time 18.5 hours.

Hydroxyl number- 26.1

g. of a mixture of methyl-epsilon-caprolactones.

Initiator 3.77 g. ethylene glycol. Catalyst 0.07 g. dibutyltin oxide. Reaction time 19 hours.

Hydroxyl number 46.8.

Carboxyl number 1.3.

Color Yellow.

Several representative substituted epsilon-caprolactones were polymerized by heating to various temperatures with an amount of ethylene glycol calculated to yield an average molecular Weight of 2200 Without a catalyst and with representative concentrations of the catalysts indicated in the table below. The catalyst concentrations are in terms of percent by weight of lactone and the procedure in each polymerization was to add the catalysts after the reactants had reached the indicated temperature. The

progress of the polymerization was followed, and polymerization time was determined, by means of the refractive index, which becomes constant when polymerization is complete.

Catalyst Epsilon-Oaprolactone Catalyst Concen- 'Iempera- Time,

tration, ture, 0. hrs. Percent Mixed Alphaand None 170 102 epsilon-methyl.

Do Dibutyltin wide. 0.1 170 2 do 0.05 170 4 -do 0.01 170 7. 5

Do do 0. 1 150 6' Do ..do 0.05 150 11.25

Dodo 0.01 150 21 Do. do 0.1 22

Do. do 0.05 130 21 Dodo 0.01 130 54 Do Dllauryltin uxlde 0.1 170 6 Do--- Di-n-butyltin di- 0.1 170 4. 5

chloride.

Do..- Tri-n-butyltin 0. 1 170 3. 75

acetate.

Do Tri-n-butyltin 0.1 170 5 o hydroxide.

Do Tetraphenyltiu.-. 0.1 170 5 Beta, delta-dimethyl- Dibutyltin 0xide 0.05 170 0.75 Gamma-methyl 0. 05 170 1 Mixed betaand do 0.05 170 0. 75

delta-methyl. Mixed alphaand Lead 2-ethyl- 0. 1 170 10. 25

epsilon-methyl. hexoate.

D0... Lead salicylate. 0. 1 170 20' Do Lead benzoate-.. 0.1 170 10 Beta, delta-di- Lead 2-et yl- 0.05 170 5. 5

meth hexoate Gamma-methyl do 0. 05 170 3. 25 Mixed betaand do 0.05 170' 5. 5 delta-methyL Mixed alphaand Manganese acetate 0. 1 170 10. 2o

epsilon-methyl.

The data in this table illustrates the remarkable efiicacy of the preferred catalysts in accelerating the polymerization of the more difficultly polymerizable lactones.

It is apparent that various modifications will readily occur to those skilled in the. art upon reading this description. All such modifications are intended to be included within the scope of the invention as defined in the accompanying claims.

We claim:

1. 'In a method of preparing a polyester by reacting, at a temperature up to about 300 C., a lactone having from six to eight carbon atoms in the ring with an organic compound. having at least one reactive site capable of opening the lactone ring in a radical selected from the group consisting of hydroxyl and amino radicals attached thereto, the improvement which comprises carrying out the reaction in the presence of between about 0.001 and 1% by weight, based on the weight of lactone, of a catalyst selected from the group consisting of organic tin compounds having at least one carbon to tin bond and carboxylic acid salts of lead and manganese.

2. In a method of preparing a polyester by reacting, at a temperature up to about 300 C., a lactone having six carbon atoms in the ring with an organic compound having at least one reactive site capable of opening the lactone ring in a radical selected from the group consisting of hydroxyl and amino radicals attached thereto, the improvement which comprises carrying out the reaction in the presence of between about 0.001 and 1% by weight, based on the weight of lactone, of an organic tin compound selected from the group consisting of compounds having one of the general formulae:

and

in which the Xs are members selected from the group consisting of alkyl, aryl, aralkyl and aryloxy radicals and the X"s are members selected from the group consisting of alkyl, aryl, aralkyl, acyloxy, halogen and hydroxy radicals.

3. Method defined in claim 2 wherein the organic tin compound is a dialkyl tin oxide.

4. Method defined in claim 2 wherein the organic tin compound is a dialkyl tin dichloride.

5. Method defined in claim 2 wherein the organic tin compound is a trialkyl tin acetate.

6. Method defined in claim 2 wherein the organic tin compound is a trialkyl tin hydroxide.

7. Method defined in claim 2 wherein the organic tin compound is a tetraaryl tin.

8. In a' method of preparing a polyester by reacting, at a temperature up to about 300 C., an epsilon-caprolactone with an organic compound having at least one radical selected from the group consisting of hydroxyl and amino radicals attached thereto, the improvement which comprises carrying out the reaction in the presence of between about 0.001 and 1% by weight, based on the weight of lactone, of a manganese salt of a carboxylic acid.

9. In a method of preparing a polyester by reacting, at a temperature up to about 300 C., an epsilon-caprolactone with an organic compound having at least one radical selected from the group consisting of hydroxyl and amino radicals attached thereto, the improvement which comprises carrying out the reactionin the presence of 10. A method of preparing a polyester which comprises heating a lactone having from six to eight carbon atoms in the ring with an organic compound having at least one reactive site capable of opening the lactone ring in a radical selected from the group consisting of hydroxyl and amino radicals attached thereto, to a temperature within the range of about 50 to about 300 C. in the presence of between about 0.001 and 1% by weight, based on the Weight of lactone, of a catalyst selected from the group consisting of organic tin compounds having at least one carbon to tin bond and carboxylic acidsalts of lead and manganese. i

11. A method of preparing a polyester which comprises heating a lactone having six carbon atoms in the ring with an initiator to a temperature within the range of about 50 to about 300 C. in the presence of between about 16 0.001 and 1% by weight, based onthe weight of lactone, of an organic tin compound selected from the group consisting of compounds having one of the general formulae:

SnO

and

X x x x in which the X's are members selected from the group consisting of alkyl, aryl, aralkyl and aryloxy radicals and the X"s are members selected from the group consisting of alkyl, aryl, aralkyl, acyloxy, halogen and hydroxy radicals.

12. Method defined in claim 11 wherein the organic tin compound is a dialkyl tin oxide.

13. Method defined in claim 11 wherein the organic tin compound is a dialkyl tin dichloride.

14. Method defined in claim 11 wherein the organic tin compound is a trialkyl tin acetate.

15. Method defined in claim 11 wherein the organic tin compound is a trialkyl tin hydroxide.

16. Method defined in claim 11 wherein the organic tin compound is a tetraaryl tin.

17. A method of preparing a polyester which comprises heating an epsilon-caprolactone with an organic compound having at least one radical selected from the group consisting of hydroxyl and amino radicals attached thereto, to a temperature within the range of about 50 to about 250 C. in the presence of between about 0.001 and 1% by weight, based on the weight of lactone, of :1

- manganese salt of a carboxylic acid.

18. A method of preparing a polyester which comprises heating an epsilon-caprolactone with an organic compound having at least one radical selected from the group consisting of hydroxyl and amino radicals attached thereto, to a temperature within the range of about 50 to about 250 C. in the presence of between about 0.001 and 1% by weight, based on the weight of lactone, of a lead salt of a carboxylic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,153,801 Hovey et al Apr. 11, 1939 2,361,036 Kung Oct. 24, 1944 2,455,731 Caldwell Dec. 7, 1948 2,555,385 Watson June 5, 1951 2,720,505 Caldwell et a1 Oct. 11, 1955 2,720,507 Caldwell Oct. 11, 1955 

1. IN A METHOD OF PREPARING A POLYESTER BY REACTING, AT A TEMPERATURE UP TOI ABOUT 300* C,. A LACTONE HAVING FROM SIX TO EIGHT CARBON ATOMS IN THE RING WITH AN ORGANIC COMPOUND HAVING AT LEAST ONE REACTIVE SITE CAPABLE OF OPENING THE LACTONE RING IN A RADICCAL SELECTED FROM THE GROUP CONSISTING OF HYDROXYL AND AMINON RADICALS ATTACHED THERETO, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT THE REACTION IN THE PRESENCE OF BETWEEN ABOUT 0.001 AND 1% BY WEIGHT, BASED ON THE WEIGHT OF LACTONE, OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF ORGANIC TIN COMPOUNDS HAVING AT LEAST ONE CARBON TO TIN BOND AND CARBOXYLIC ACID SALTS OF LEAD AND MANGANESE. 